JP2008141882A - Multiaxial synchronous drive circuit for stepping motors - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiaxial synchronous drive circuit for stepping motors which synchronously controls multiple stepping motors in a drive system using multiple axes. <P>SOLUTION: The multiaxial synchronous driver circuit is constructed of multiple constant-current drive circuit portions 5a, 5b (a) and an excitation sequence control circuit 2 (b). The constant-current drive circuit portions 5a, 5b respectively include output stages 6a, 6b that are connected to multiple stepping motors M1, M2 synchronously operated in one drive system and control driving of the stepping motors M1, M2. The constant-current drive circuit portions 5a, 5b are provided in units of stepping motors. The excitation sequence control circuit 2 receives command pulses CW, CCW for causing the stepping motors M1, M2 to step and synchronously outputs excitation sequences to the output stages 6a, 6b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-axis synchronous drive circuit for a stepping motor that operates a plurality of stepping motors that operate in a synchronized manner in one drive system.

  In precision measuring instruments, inspection devices, and precision processing equipment, uniaxial ball screws are widely used in mechanisms that move in a uniaxial (eg, horizontal) direction. Recently, the object to be measured tends to increase in size with the aim of further improving productivity efficiency. With the increase in the size of the object to be measured, the ball screw that has been used for horizontal movement also has a problem that the horizontal balance is poor and the movement speed cannot be increased due to insufficient torque when the single screw configuration is used.

  Therefore, in order to solve such unbalanced horizontal balance and torque shortage, it has been attempted to use two ball screws in one drive system, and recently, a two-axis drive system has been frequently adopted. I came. In such a case, it is necessary to drive the stepping motor connected to each ball screw while being completely synchronized.

Therefore, in order to carry out the stepping motor drive of such a biaxial drive system in a completely synchronized state, as shown in FIG. 2, each stepping motor (52a) (52b) is individually supplied with a stepping motor drive circuit (50a) ( 50b), command pulses (CW / CCW) from the external device (controller) (51) are supplied to the respective stepping motor drive circuits (50a) (50b), and each stepping motor (52a) (52b) is supplied. I tried to drive them synchronously. However, in such a method, the same command pulse (CW / CCW) is input to the stepping motor drive circuits (50a) and (50b) at the same time, but the component parts of the stepping motor drive circuits (50a) and (50b) vary. Due to variations in the stepping motors (52a) and (52b) themselves (individual variations in the DC resistance value and inductance of the windings and the effects of regenerative voltage due to this), slight deviations and synchronization deviations inevitably occur in the horizontal balance of the drive system. And
(a) Twist occurs in the moving table (54) on which the workpiece conveyed by the ball screw (53a) (53b) is placed.
(b) The speed following performance of the ball screw (53a) (53b) is deteriorated.
The phenomenon that occurred. In addition, the higher the torsion of the moving platform (54) on which the workpiece is placed, the slower the maximum speed to follow, and if this is severe, the stepping motors (52a) (52b) may be stepped out. It was.

Therefore, an attempt is made to execute the two-axis drive by eliminating the variation of the components of the stepping motor drive circuits (50a) and (50b), and the control is performed by the external device (controller) (60) as shown in FIG. In addition, the output of one stepping motor drive circuit (50) was branched into two and input to the respective stepping motors (52a) and (52b) to realize synchronous driving. However, in this case, since the two stepping motors (52a) and (52b) are synchronously driven simultaneously by one stepping motor driving circuit (50), this stepping motor driving circuit (50) has twice the rating. A driving current flows, and such a driving method leads to damage of the stepping motor driving circuit (50).
JP 2006-60925

  Accordingly, the present inventors set the problem to be solved by developing a multi-axis synchronous drive circuit for a stepping motor capable of synchronously controlling a plurality of stepping motors in a drive system using multiple axes as well as two axes.

The multi-axis synchronous drive circuit of the stepping motor of the present invention is
(a) An output stage (6a) connected to a plurality of stepping motors (M1), (M2), which operate synchronously in one drive system, and which controls driving of the stepping motors (M1, M2, ...) A plurality of constant current drive circuit units (5a) (5b) provided for each of the stepping motors (M1), (M2),
(b) Excitation sequence that receives the input of command pulses (CW, CCW) to step the stepping motors (M1), (M2), etc., and outputs them in synchronization with the output stage (6a) (6b). And a control circuit (2).

  As described above, in the present invention, the constant current drive circuits (5a) (5b)... Are provided for each stepping motor (M1) (M2). The effect of regenerative voltage (back electromotive force generated by rotation of stepping motors (M1) (M2) ...) can be individualized, and constant current control can be performed individually, so stable multi-axis drive control ( 2-axis drive control) is now possible.

  The present invention will be described below with reference to the illustrated embodiments. In the present invention, a multi-axis drive system using two or more ball screws in one drive system is used to drive a stepping motor connected to the ball screw in complete synchronization. This will be described as a representative example. In the following description, the ball screw connected to the stepping motor as the load side will be mainly described. However, the present invention is not limited to this, and can be applied to belt driving with a gear or pulley connected to the stepping motor. Needless to say. The load-side ball screw stage of the present invention is as shown in FIGS.

In this embodiment circuit (two axes; see FIG. 1),
(B) Interface circuit (1) (for example, photocoupler circuit) that receives command pulses (CW pulse, CCW pulse) from an external controller (pulse generator),
(B) Control of the stepping of each stepping motor (M1) (M2) [In other words, switching control of the output stage (6a) (6b) of the constant current output circuit section (5a) (5b) is performed) Sequence control circuit (2),
(C) Each stepping motor (M1) (M2) is connected to each stepping motor (M1) (M2), and the total current (2ioa) (2iob) flowing through each stepping motor (M1) (M2) is controlled to follow the same reference voltage. Constant current output circuit units (5a) (5b) and step drive
(D) It is composed of a constant current output circuit section (5a) (5b) and a direct current supply section (3) for supplying a direct current to the constant current output circuit section (5a) (5b).

  The interface circuit (1), the excitation sequence control circuit (2), and the direct current supply unit (3) are shared, while the constant current output circuit units (5a) and (5b) are connected to the stepping motors (M1) (M1) ( M2) is provided individually and is synchronized with the on / off commands of the power elements of the output stages (6a) and (6b). As the stepping motors (M1) and (M2) to be controlled, a five-phase stepping motor will be described as a representative example, but the present invention is not limited to this.

  For example, a photocoupler circuit is used as the interface circuit (1), and it receives a command pulse (CW pulse, CCW pulse) and outputs a pulse signal to the excitation sequence control circuit (2). In response to this signal, the excitation sequence control circuit (2) outputs an excitation pattern corresponding to the excitation pattern designation address to each output stage (6a) (6b). As a result, the power elements of the output stages (6a) and (6b) are turned on / off according to the sequence, and the stepping motors (M1) and (M2) are switched in excitation and stepped.

  DC current supply unit (3) is connected to a commercial power supply (AC; AC input), fuse (31a) (31b) for protecting constant current output circuit unit (5a) from overload, filter for noise removal Circuit (32), connected to the filter circuit (32), and composed of a rectifier circuit (33) that rectifies alternating current into direct current, and direct current is separately supplied to the constant current output circuit sections (5a) and (5b). It comes to supply.

  The constant current output circuit unit (5a) (5b) is branched and connected to the direct current supply unit (3) as described above, but the constant current output circuit unit (5b) is connected to the constant current output circuit unit ( Since the circuit configuration is the same as that of 5a), the constant current output circuit unit (5a) will be described as a representative example in order to avoid complicated description. For the same members, the constant current output circuit portion (5b) is given the same number, which is different from the letters a and b, and is replaced with the description. However, there is generally a slight error between them due to the components.

The constant current output circuit (5a)
(a) Chopper (9a) for chopping (on / off) the rectified direct current according to the control by the constant current control circuit (51a) described later and supplying the current value according to the control value of the constant current control circuit (51a) [In this embodiment, a power MOS FET is used. ],
(b) Supply current (i1a) connected between the ground (Ga) connected to the zero volt line (Za) of the constant current output circuit (5a) and the positive line (+) input side. First capacitor (C1a),
(c) Flywheel diode (D1a) connected between the zero volt line (Za) of the constant current output circuit section (5a) and the output side of the chopper (9a),
(d) A reactor (L1a) provided in series on the output side of the chopper (9a), for smoothing the chopped current in cooperation with the capacitor (C2a),
(e) A driver terminal connected to the stepping motor (M1) is provided, connected to the output side of the reactor (L1a) and the zero volt line (Za), and an output stage (6a ),
(f) A small sense resistor (R1a) (R2a) connected in series with the output stage (6a),
[In this embodiment, the sense resistor is composed of a first sense resistor (R1a) and a second sense resistor (R2b), and the first sense resistor (R1a) is on the (−) side of the first capacitor (C1a). And the second sense resistor (R2a) are connected in series, and the second sense resistor (R2a) is connected to the (−) side of the output stage (6a) and the second capacitor (C2a) [or the first sense resistor ( R1a)]. In this case, sensing is performed by both the first sense resistor (R1) and the second sense resistor (R2), and the current to be detected is the total current (2ioa) for operating the stepping motor (M1), that is, the operating current. (i1a + i2a-i3a). In other words, the sense resistor (R1a) is a supply current that circulates from the first capacitor (C1a) to the chopper (9a), the reactor (L1a), the second capacitor (C2a), and the sense resistor (R1a) in the clockwise direction in the figure. (i1a) is detected, and the sense resistor (R2a) detects the excitation current (i2a) flowing in the zero volt line (Za) direction from the (+) side through the output stage (6a) and the stepping motor (M1). A drive current (i2a-i3a), which is the sum of the electromotive current (i3a) generated in the stepping motor (M1) during operation and flowing in the opposite direction, is detected. ]
(g) Driving voltage application unit (DVa) for passing a constant current to the stepping motor (M1) [The driving current (i2a-i3a) is less likely to flow as the rotational speed of the stepping motor (M1) increases, Since the circuit is a constant current circuit, the motor drive voltage application unit (DVa) increases the motor drive voltage as the rotational speed increases so that the constant current flows to the stepping motor (M1). ]
(h) A second capacitor (between the output side of the reactor (L1a) and the connection portion of the sense resistor (R1a) (R2a) for supplying the exciting current (i2a) to the output stage (6a) ( C2a).

  As described above, the output stage (6a) has a switching element as its main configuration, and in this embodiment, a power MOS • FET is used, and has the following known configuration. The output stage transistors, which are switching elements of the output stage (6a), are divided into five sets, and two sets are connected in series, and the five sets are connected in parallel to form the output stage (6a). Then, the output stage transistor is connected to a connecting portion of the winding connected in a ring shape of the stepping motor (M1). By controlling these switching means on / off according to the sequence, the stepping motor (M1) can be advanced according to the sequence.

  The current (i1a) is a supply current for raising and lowering the driving voltage (DVa voltage) of the stepping motor (M1) and charging the second capacitor (C2a), and the current (i2a) is the second capacitor (C2a). This is an exciting current of the stepping motor (M1) generated by this discharge, and circulates as a second capacitor (C2a), an output stage (6a), and a second sense resistor (R2a) as shown by a broken line in the figure. The current (i3a) is an electromotive current generated by the rotational motion of the rotor of the stepping motor (M1), and is a surplus current in the direction opposite to the excitation current (i2a). The electromotive current (i3a) circulates through the diode of the output stage (6a) to the second capacitor (C2a), the second sense resistor (R2a), and the output stage (6a). As a result, the drive current (i2a-i3a) obtained by subtracting the electromotive current (i3a) from the excitation current (i2a) flows through the sense resistor (R2a). Then, the chopper (9a) is controlled by the constant current control circuit (PWM) by the sum (V1a + V2a) of the detection voltages detected by the sense resistors (R1a) and (R2a).

  Next, the operation of the circuit of the present invention will be described. When the command pulse (CW / CCW) is input to the excitation sequence control circuit (2) via the interface circuit (1), the command pulse (CW / CCW) is counted and the excitation pattern based on the address is sequentially output. This is branched in the middle and output to the output stage (6a) (6b). In the output stages (6a) and (6b), the output stage switching elements are synchronized and turned on / off according to this excitation pattern, and the stepping motors (M1) and (M2) are synchronously divided and driven according to the sequence.

  Here, there are slight errors in the component parts of the constant current output circuit sections (5a) and (5b) and the stepping motors (M1) and (M2) that are individually provided, and the stepping motors (M1) and (M2) are stepped respectively. The total driving current (2ioa) (2iob) is slightly different. However, in the present invention, the constant current output circuit section (5a) (5b) is provided for each stepping motor (M1) (M2), so that current supply corresponding to slightly different total currents (2ioa) (2iob) is possible. Made. The excitation pattern for stepping the stepping motors (M1) and (M2) is branched and input to the output stages (6a) and (6b) that directly control the stepping motors (M1) and (M2). Stepping motors (M1) and (M2) are individually synchronized with the effects of individual variations in DC resistance and inductance of motor windings and regenerative voltage (back electromotive voltage generated by rotation of the stepping motor). Can be driven stably in multi-axis step.

Circuit diagram of stepping motor to which the present invention is applied Circuit diagram of conventional example Circuit diagram of conventional example

Explanation of symbols

(M1) (M2) ... Stepping motor
(io) ... Current to operate the stepping motor = Operating current
(i1) ... Supply current
(i2) ... Excitation current
(i2-i3) ... Drive current
(i3) ... electromotive current
(2io) ... Total current
(M1) (M2) ... Stepping motor
(5a) (5b) ... Constant current drive circuit
(6a) (6b) ... Output stage

Claims (1)

(a) A plurality of constant current drive circuits connected to a plurality of stepping motors that operate synchronously in one drive system, each having an output stage for driving and controlling the stepping motor, and provided for each stepping motor And
(b) An excitation sequence control circuit that receives an input of a command pulse for advancing the stepping motor, branches to the output stage, and individually outputs an excitation sequence in synchronization with each other.
(c) Stepping motor multi-axis synchronous drive circuit.

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